Image intensifier devices are used to amplify low intensity light or convert non-visible light into readily viewable images. Image intensifier devices are particularly useful for providing images from infrared light and have many industrial and military applications. For example, image intensifier tubes are used for enhancing the night vision of aviators, for photographing astronomical bodies and for providing night vision to sufferers of retinitis pigmentosa (night blindness).
Examples of three types of image intensifying devices are image intensifier tubes, solid-state CMOS and CCD sensors, and hybrid EBCCD/CMOS (Electronic Bombarded CCD or CMOS sensor).
A current state of the art image intensifier, as an example, is the Generation III (GEN III) image intensifier tube exemplified in U.S. Pat. No. 5,029,963 to Naselli, et al., entitled REPLACEMENT DEVICE FOR A DRIVER'S VIEWER and U.S. Pat. No. 5,084,780 to Phillips, entitled TELESCOPIC SIGHT FOR DAYLIGHT VIEWING. The GEN III image intensifier tube in both cited references is of the type currently manufactured by ITT Corporation, the assignee herein.
An image intensifier tube, or a solid state device, typically includes a photo cathode, a gallium arsenide (GaAs) active layer and a microchannel plate (MCP) positioned within a vacuum housing. Infrared energy, for example, may impinge upon the photo cathode and be absorbed in the GaAs active layer, thereby resulting in generation of electron/hole pairs. The generated electrons are then emitted into the vacuum housing and amplified by the MCP.
Once electrons exit the photo cathode, the electrons are accelerated toward an input surface of the MCP by a difference in potential between the input surface of the MCP and the photo cathode, which may be approximately 300 to 900 volts. As the electrons bombard the input surface of the MCP, secondary electrons are generated within the MCP. The MCP may then generate several hundred electrons for each electron entering the input surface. The MCP is also subjected to a difference in potential between its input surface and its output surface, which is typically about 1100 volts. This potential difference enables electron multiplication in the MCP.
As the multiplied electrons exit the MCP, the electrons are accelerated through the vacuum housing toward a phosphor screen (for example) by yet another difference in potential between the phosphor screen and the output surface of the MCP of approximately 4200 volts.
Accordingly, a power supply is generally used to provide the various potential differences of voltage (such as V1, V2 . . . Vn) to the image intensifier device. This power supply may be a single integrated unit that provides all the required voltages, or multiple power supplies may be used, as required for the specific application. It will be appreciated, therefore, that as used herein the term “power supply” refers to one integrated unit or multiple units.
The image intensifiers may easily be stolen or lost, thereby allowing them to fall into unfriendly or unauthorized hands. Lost or stolen image intensifiers may also cause problems to manufacturers producing these devices, because image intensifiers are subject to export restrictions.
The present invention addresses this problem and provides several solutions.